a free fall dive from earth's stratosphere, 23 miles above new mexico. >> right now i'm really confident in my team, confident in my management, and last but not least, i'm confident in myself. >> reporter: baumgartner will plunge further and fall faster than anybody in history. describe the red bull jump. what is it? >> within the first 30 seconds, 'm going to accelerate so fast that i'm going to break the speed of sound. >> reporter: break the speed of sound the first time ever for a person. >> yes, without aircraft, in free fall as a human person. >> reporter: baumgartner will rise in a capsule lifted by a helium balloon that's 55 stories tall at liftoff. three times bigger than any balloon ever used in the man flight. the assent will take two and a half hours. he'll jump from 120,000 feet or higher, a virtual vacuum. there's almost no air, water, or wind. the temperature will be minus 70 degrees. within 35 second, his top speed is expected to approach 700 miles per hour. mach 1. >> mach 1.0. >> shock waves are a concern. >> reporter: dr. jonathan clark, the mission's medical director